The invention concerns a container lid with a sealing device. It is known that, in order to protect substances held within containers, the containers are closed by lids which seal in the area where the container and the lid match.
Thus, for instance, containers for industrial use, which are commonly called barrels and are meant to contain especially lubricating oils, hydrocarbon liquids, acids and the like, are closed by lids having a shaped annular ridge, through which they are solidly riveted into the upper rim of the barrel. Such lids achieve an air- and water-tight seal, but present the inconvenience that, once the barrel has been emptied, it cannot be re-used. In fact, in order to re-use it, it is necessary to clean its inside, after the lid has been removed by cutting off the annular rim which attaches it to the barrel. This operation deforms the rim of the barrel which then becomes unsuited to receive other lids and, therefore, cannot be re-used. The barrel can be used at best as a generic container, but it presents the inconvenience that, due to the deformed rim, it can also be dangerous, particularly if the barrel is made of metal.
If the barrel is meant to contain substances in grain or powder form, such as, dyes, bonding agents and, substances which do not require an absolutely tight seal, lids are used which present one or more perimetral rims which, when pressed, snap because of elastic deformation into matching rims of the barrel. In this case, since the lid can easily be applied and removed, it offers the advantage of making it possible to re-use the barrel, since it is easy to reach its interior for cleaning purposes without damaging the rim of the container on which the lid is applied. The inconvenience presented by this type of lids is that they do not hermetically close the container.
In the special branch of the manufacture of lead-acid storage batteries, it is a known fact that the lids sealing the containers which hold the elements of the battery must perform two important tasks.
The first task is to guarantee the tight sealing of the container thereby preventing the spilling out of the electrolyte contained therein, which, considering its high degree of corrosive power, may cause considerable damage.
A second but not by any means minor tasks is that they must allow for the lengthening of the poles, particularly of the positive pole which, because of electrochemical phenomena, becomes longer during the life span of the battery. Thus the poles are prevented from pressing against the lid, while the tight sealing of the lid itself is safeguarded.
As far as tightness is concerned, it is guaranteed either by sealing the lid to the container holding the poles of the accumulator battery by means of bonding agents, or by creating rims on the lid and the container, which rims come into mutual contact through special profiles matching each other.
On the other hand, as far as the extension of the poles is concerned, it is allowed for by using bonding agents with a very high yield point or by suitably shaping the surface of the lid, or by shaping the seats of the poles to make them elastic and deformable.
These known methods, while being praise worthy for solving both the problem of the hermetic seal and that of the lengthening of the poles, present some inconveniences.
Concerning the method of obtaining the hermetic seal through the use of bonding agents with a high yield point, it presents the inconvenience that, when it becomes necessary to remove the lid in order to perform maintenance operations on the accumulator battery, the removal is difficult. In fact, it is necessary to remove the bonding seam, which often leads to damage to the container lid. The method which uses specially shaped matching rims between the lids and the containers, presents the inconveniences that lids and containers are not interchangeable, and that costly and complex moulds are necessary to manufacture them.
Concerning the method of deformable lids and pole seats, the manufacture of lids with surfaces having special shapes requires the use of complex moulds, and does not solve the problem in lids having a limited width in comparison with their length, since such lids present an insufficient degree of elasticity. In addition, the production of elastic and deformable seats for the poles is not cost-efficient because of the expense involved in the moulds necessary for such production.